1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device, a base constituting the piezoelectric/electrostrictive device, and a method of producing the piezoelectric/electrostrictive device.
2. Description of the Background Art
As one form of piezoelectric/electrostrictive device, there is known a piezoelectric/electrostrictive device of a form that includes a base having a pair of movable parts that are arranged in parallel with each other to oppose each other and a connecting part that connects the two movable parts with each other at one end thereof as well as a piezoelectric/electrostrictive element disposed on an outer side surface of at least one of the two movable parts of the base, as disclosed in the specification of European Patent EP1017116A2.
The piezoelectric/electrostrictive device of such a form has a function of operating the movable parts caused by the displacement operation of the piezoelectric/electrostrictive element or a sensing function of sensing the displacement of the movable parts input from the side that is sensed, with the use of the piezoelectric/electrostrictive element. By effectively using these functions, the piezoelectric/electrostrictive device is used in a wide range of fields such as described below.
Namely, the piezoelectric/electrostrictive devices of such a form are used as active elements such as various transducers, various actuators, frequency region functional components (filters), transformers, vibrators and resonators for communication or mechanical power, oscillators, and discriminators, various sensor elements such as supersonic wave sensors, acceleration sensors, angular velocity sensors, impact sensors, and mass sensors, and various actuators that are put to use for displacement, positioning adjustment, and angle adjustment mechanism for various precision components of optical instruments and precision apparatus.
Meanwhile, the piezoelectric/electrostrictive device of such a form is generally composed of a base and at least one piezoelectric/electrostrictive element, and these are bonded to each other via an adhesive. Further, the base is composed of construction members that constitute a pair of movable parts and another construction member that connects these two construction members, and these construction members are bonded to each other via an adhesive.
Thus, the piezoelectric/electrostrictive device having such a form has a large number of construction members, so that the device is produced at a high cost and through a troublesome assembling work. Moreover, since the construction members are bonded to each other via an adhesive, there arises a dispersion of adhesion between the construction members, giving rise to a fear that the device characteristics may be adversely affected.
Further, the piezoelectric/electrostrictive device having such a form is produced by adopting means for cutting a device master suitably into a large number of devices. Therefore, the piezoelectric/electrostrictive devices formed by cutting are contaminated with dusts generated at the process of cutting, cutting fluid, and organic components such as an adhesive or wax used for holding the device master at the process of cutting, so that it is not easy to clean the piezoelectric/electrostrictive device.
Further, in the case where the base is constructed with a ceramic, i.e. a sintered body formed from plural sheets of ceramic green sheet laminates, one must adopt a hard ceramic material such as zirconia, since the ceramics are liable to be split. Even if a hard ceramic material is adopted, one must choose a suitable cutting condition so as not to generate loss of the material or cracks. Furthermore, since the base is made of a hard ceramic material, the machining process is difficult and, in order to increase process capacity, one must give a careful consideration such as use of a large number of machining apparatus having different functions.
Here, the base can be constructed with a metal material; however, the metal material gives rise to an oxidized end surface by friction heat during the cutting process and burrs remain on the processed end surface, so that one must add another step of removing these. Further, the piezoelectric/electrostrictive device can be tested only after the device master is cut.
Further, the device cut out from the device master is preferably cleaned by adopting supersonic wave cleaning so that the contamination can be easily removed. However, if a strong supersonic wave is used to obtain a high cleaning effect in supersonic wave cleaning, the device may be damaged, and the piezoelectric/electrostrictive element may be broken or exfoliated from the base. For this reason, if the supersonic wave cleaning is adopted, one must select a weak supersonic wave that does not give damages to the device. However, if such a cleaning condition is adopted, a long period of time is needed in removing the contamination that has adhered at the process of cutting.
Dust generation from the piezoelectric/electrostrictive device may cause the following problems. For example, in the case where the piezoelectric/electrostrictive device is used as an actuator of a magnetic head in a hard disk drive, if dust is generated in the drive, the dust may cause crash of the floating slider onto the medium, thereby raising a fear of data destruction. Also, for the piezoelectric/electrostrictive device itself, the dust may adhere to the electrode of the piezoelectric/electrostrictive device, thereby giving rise to a fear of short circuit. For this reason, a high level of cleaning is required not only in the hard disk drive but also in the device itself.
Therefore, an object of the present invention is to solve the aforementioned problems of the prior art by allowing the base constituting the piezoelectric/electrostrictive device of that form to have an integral structure using one sheet of flat plate as an original plate.